The following disclosure relates to energy management, and more particularly to energy management of household consumer appliances, as well as other energy consuming devices and/or systems found in the home. The present disclosure finds particular application to a hydrocarbon fueled hot water heater.
Home energy management (HEM) systems are becoming a key to reducing energy consumption in homes and buildings, in a consumer friendly manner. Existing HEMs are commonly placed in one of two general categories: In the first category, the HEM is in the form of a special custom configured computer with an integrated display, which communicates to devices in the home and stores data, and also has simple algorithms to enable energy reduction. This type of device may also include a keypad for data entry or the display may be a touch screen. In either arrangement, the display, computer and key pad (if used) are formed as a single unit. This single unit is either integrated in a unitary housing, or if the display is not in the same housing, the display and computer are otherwise connected associated upon delivery from the factory and/or synchronized or tuned to work as a single unit. In the second category, the HEM is in the form of a low cost router/gateway device in a home that collects information from devices within the home and sends it to a remote server and in return receives control commands from the remote server and transmits it to energy consuming devices in the home. In this category, again, as in the first, the HEM may be a custom configured device including a computer and integrated/associated display (and keypad, if used) designed as a single unit. Alternately, the HEM maybe implemented as home computer such as laptop or desktop operating software to customize the home computer this use.
Key functions of a HEM system can include:                Creates a network of energy consuming devices within the home,        Measures the consumption of the whole home/building or individual devices,        Records and stores energy consumption information in a database, and        Enables consumer interface with all energy consuming devices in a home to:                    view consumption data of individual devices            set preferences for operation of energy consuming devices at different times during the day or at different energy pricing levels            control/program energy consuming devices.                        
While the integration of a HEM to existing electrical devices in a residence is relatively straightforward, hydrocarbon fueled devices such as water heaters and or furnaces present a more challenging situation because they do not consume electricity as their primary energy source. A basic hot water heater generally includes a water reservoir, a heating element and a thermostat or other temperature controller that controls the burner to maintain a set temperature of the water in the reservoir. In general, the temperature of the water is maintained at a relatively constant level corresponding to a set point of the thermostat, for example 140 degrees F., until it is needed. As hot water is dispensed from the reservoir, cold water is admitted thereby lowering the temperature of the water. Once the temperature drops below the set point of the thermostat, the heating element is activated to raise the temperature of the water. Burner comes on to maintain temperature too.
Gas hot water heaters burn gas, such as natural gas or propane, to heat water. Typically, the amount of gas used by the hot water heater is not readily ascertainable unless the gas water heater is the only gas-powered appliance in the home, and such scenario is not common. Even if the gas water heater is the only gas-powered appliance in the home, the gas consumption of the unit is generally not known to the consumer until a monthly bill is issued for the gas used during the previous month. The lack of a reliable way to determine gas usage of hydrocarbon fueled hot water heaters can frustrate consumers' attempts to control energy usage of such hot water heaters, and prevent their integration into a HEM system.